1 //===-- SystemZTargetMachine.cpp - Define TargetMachine for SystemZ -------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "SystemZTargetMachine.h"
11 #include "llvm/CodeGen/Passes.h"
12 #include "llvm/Support/TargetRegistry.h"
13 #include "llvm/Transforms/Scalar.h"
14 
15 using namespace llvm;
16 
17 extern "C" void LLVMInitializeSystemZTarget() {
18   // Register the target.
19   RegisterTargetMachine<SystemZTargetMachine> X(TheSystemZTarget);
20 }
21 
22 SystemZTargetMachine::SystemZTargetMachine(const Target &T, StringRef TT,
23                                            StringRef CPU, StringRef FS,
24                                            const TargetOptions &Options,
25                                            Reloc::Model RM, CodeModel::Model CM,
26                                            CodeGenOpt::Level OL)
27     : LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL),
28       Subtarget(TT, CPU, FS),
29       // Make sure that global data has at least 16 bits of alignment by
30       // default, so that we can refer to it using LARL.  We don't have any
31       // special requirements for stack variables though.
32       DL("E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64"),
33       InstrInfo(Subtarget), TLInfo(*this), TSInfo(DL), FrameLowering() {
34   initAsmInfo();
35 }
36 
37 namespace {
38 /// SystemZ Code Generator Pass Configuration Options.
39 class SystemZPassConfig : public TargetPassConfig {
40 public:
41   SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
42     : TargetPassConfig(TM, PM) {}
43 
44   SystemZTargetMachine &getSystemZTargetMachine() const {
45     return getTM<SystemZTargetMachine>();
46   }
47 
48   void addIRPasses() override;
49   bool addInstSelector() override;
50   bool addPreSched2() override;
51   bool addPreEmitPass() override;
52 };
53 } // end anonymous namespace
54 
55 void SystemZPassConfig::addIRPasses() {
56   TargetPassConfig::addIRPasses();
57   addPass(createPartiallyInlineLibCallsPass());
58 }
59 
60 bool SystemZPassConfig::addInstSelector() {
61   addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
62   return false;
63 }
64 
65 bool SystemZPassConfig::addPreSched2() {
66   if (getOptLevel() != CodeGenOpt::None &&
67       getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
68     addPass(&IfConverterID);
69   return true;
70 }
71 
72 bool SystemZPassConfig::addPreEmitPass() {
73   // We eliminate comparisons here rather than earlier because some
74   // transformations can change the set of available CC values and we
75   // generally want those transformations to have priority.  This is
76   // especially true in the commonest case where the result of the comparison
77   // is used by a single in-range branch instruction, since we will then
78   // be able to fuse the compare and the branch instead.
79   //
80   // For example, two-address NILF can sometimes be converted into
81   // three-address RISBLG.  NILF produces a CC value that indicates whether
82   // the low word is zero, but RISBLG does not modify CC at all.  On the
83   // other hand, 64-bit ANDs like NILL can sometimes be converted to RISBG.
84   // The CC value produced by NILL isn't useful for our purposes, but the
85   // value produced by RISBG can be used for any comparison with zero
86   // (not just equality).  So there are some transformations that lose
87   // CC values (while still being worthwhile) and others that happen to make
88   // the CC result more useful than it was originally.
89   //
90   // Another reason is that we only want to use BRANCH ON COUNT in cases
91   // where we know that the count register is not going to be spilled.
92   //
93   // Doing it so late makes it more likely that a register will be reused
94   // between the comparison and the branch, but it isn't clear whether
95   // preventing that would be a win or not.
96   if (getOptLevel() != CodeGenOpt::None)
97     addPass(createSystemZElimComparePass(getSystemZTargetMachine()));
98   if (getOptLevel() != CodeGenOpt::None)
99     addPass(createSystemZShortenInstPass(getSystemZTargetMachine()));
100   addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
101   return true;
102 }
103 
104 TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
105   return new SystemZPassConfig(this, PM);
106 }
107